Ultrasound is used for imaging applications, in the clinical field for ultrasonographic investigations, for example. An ultrasound transmission/reception apparatus generally includes a plurality of acoustic transducers (e.g., example piezoelectric or microphone transducers) which are appropriately controlled to generate ultrasound pulses, and for receiving the echo generated by the ultrasounds after they have impinged on a target of interest (for example, a portion of the human body, in the case of ultrasonographic investigations).
In particular, beamforming techniques may be used for driving the acoustic transducers. During transmission, the acoustic transducers are driven with suitable relative time delays to focus the ultrasound beams generated by each acoustic transducer onto the target of interest, thus creating suitable constructive or destructive interference patterns (which is generally known and not described in detail herein). During reception, the time delays are taken into consideration while processing the signals received by a receiver device of the ultrasound transmission/reception apparatus.
As illustrated schematically in FIG. 1, an ultrasound transmission/reception apparatus 101 having a plurality of channels (six in the illustrated example, although other numbers may be used), illustratively includes a set of acoustic transducers 102. For example, the transducers 102 may be piezoelectric transducers arranged in an array, such as a linear array or a matrix array (usually one for each channel), suitably driven for generating respective ultrasound beams during a transmission phase, and further for receiving the echo of the generated ultrasounds during a subsequent reception phase which is temporally distinct from the transmission phase.
The apparatus 101 further illustratively includes a driving device 103 coupled to the acoustic transducers 102 for supplying suitable electrical driving signals and controlling an operating state of the acoustic transducers 102. A receiver device 104 is coupled to the acoustic transducers 102 during the reception phase for managing reception of the ultrasound echoes received on the various channels.
In particular, the driving device 103 also includes a control unit 105 designed or configured to suitably time the phases of transmission and reception and to manage biasing of the acoustic transducers 102 during the same transmission and reception phases. A plurality of pulse-generation units 106 are each coupled to a respective channel and are managed by the control unit 105 for supplying respective driving signals Sd, typically high-voltage impulse signals, to the corresponding acoustic transducers 102. The driving signals Sd have suitable waveforms and are appropriately delayed in time with respect to one another (for example, with a delay increasing from a first channel with the shortest delay (e.g., a zero delay) to a second channel with the highest delay) to cause generation of ultrasound beams directed towards a common target B. The increase in delay is represented schematically by the arrow in FIG. 1. The delays may be linearly decreasing, and it may also be possible to have different delay configurations, e.g., with the longest delay on a central channel and delays that decrease towards the outer channels.
The receiver device 104 in turn includes a plurality of receiving units 107 which are selectively coupled (e.g., through switching elements not shown in the present example) to the acoustic transducers 102 during reception of the ultrasound echoes for processing (e.g., via filtering and amplification operations), and potentially converting from analog to digital to enable subsequent processing thereof. The detected ultrasound signals are received with different delays due to the different distances covered starting from the common target B. The receiver device 104 further illustratively includes a reconstruction unit 108 that is coupled to the receiving units 107 and is designed or configured to suitably compensate the delays and synchronize the ultrasound signals received by the various channels to enable subsequent imaging, e.g., ultrasonographic imaging.
Conveniently, the driving device 103 may be an integrated device, for example in the form of an integrated circuit chip with a package. More particularly, the driving device 103 and the receiver device 104 may be integrated within a same chip. The ultrasound transmission/reception apparatus 101 is further coupled to an external supervision unit 109, e.g., a management unit of a sonographer in which the ultrasound transmission/reception apparatus 101 is used, which manages operation thereof according to the ultrasonographic investigations that are to be carried out.
The external supervision unit 109 (which may include, for example, a microprocessor, a microcontroller, an FPGA or similar processing unit) is distinct from the control unit 105 of the driving device 103 (each has respective processing capability), and co-operates with the same control unit 105 (and with the reception device 104) for implementing a control system 100. The control system 100 controls operation of the ultrasound transmission and reception by the ultrasound transmission/reception apparatus 101.
In particular, the control unit 105 of the driving device 103 is configured to control the acoustic transducers 102 in the following different operating states, according to the operations to be performed. In an inactive state (i.e., a “clamp” or “setup” state), the acoustic transducers 102 are inactive (e.g., the acoustic transducers 102 are connected to a ground reference voltage). The inactive state may correspond to a wait phase prior to a subsequent phase of transmission or reception of ultrasounds, as described in greater detail below.
In a transmission state, the acoustic transducers 102 are biased by the high-voltage driving signals Sd, with appropriate waveforms, for generation of the ultrasound beams. In a reception state, the acoustic transducers 102 are configured to receive the echo generated by the ultrasound beams during the previous transmission phase.
Typically, after the transmission phase the acoustic transducers 102 are set in the inactive state for a pre-set time (which generally has the function of eliminating residual vibrations or oscillations on the acoustic transducers 102). After this, the same acoustic transducers 102 are set in the reception state. Following the reception phase, the acoustic transducers 102 are again set in the inactive state, waiting for the subsequent transmission phase (the inactive phase may be used for operations of setup of the ultrasound transmission/reception apparatus 101). The foregoing operating states are repeated in a periodic, cyclic way during operation of the ultrasound transmission/reception apparatus 101.
While the timing of the remaining state transitions may be managed internally, the ultrasound transmission/reception apparatus 101 receives certain information externally, in particular from an external supervision unit 109. First, an indication of the start instant START is provided, i.e., when the transmission phase is started and the previous inactive phase of the acoustic transducers 102 is terminated. Second, an indication of the stop instant STOP is provided, i.e., when the reception phase is terminated and the acoustic transducers 102 shift again to the inactive phase.
The external supervision unit 109 makes these determinations based upon acoustic environment and of the operating requirements, which are linked to the nature of the sonographic investigation, for example. This is done at the start of each cycle of the transmission phase and for the time interval during which the acoustic transducers 102 are to receive the ultrasound echoes. For example, the time of reception of the ultrasound echoes may be linked to the depth from the surface at which the target B of the sonographic investigation is located.
The present Applicant has realized that the mode of externally supplying the start START and stop STOP indications to the transmission/reception apparatus 101 may be significant. In particular, typical approaches contemplate that the START and STOP indications are supplied via respective commands received through a serial communication interface, for example an SPI or I2C interface, or similar data-communication interface.
The present Applicant has also realized that use of a similar communication interface requires, however, a considerable time interval for reading and interpreting the commands, which is intrinsic to the communication protocol used. This time interval has to be considered and correctly evaluated by the external supervision unit 109, also considering the fact that, in an ultrasound system, the correct calculation of the times of transmission/reception/inactivity is important for proper operation.
Furthermore, the activity of the serial clock required for operation of the communication protocol may disturb the operations of reception of the ultrasound echoes. In particular, this may result in errors in reception. In this regard, it should be noted that the electrical signals associated with ultrasound echoes typically have a small amplitude. Thus, in general, use of this mode of transmission of the command indications may be susceptible to errors and malfunctioning.
Other approaches send appropriate digital command signals from the external supervision unit 109 to the ultrasound transmission/reception apparatus 101, each of which encodes a respective operating phase of transmission, reception, and inactivity. The present Applicant has realized, however, that this approach entails the risk of the digital command signals not being correctly received and/or correctly interpreted. Moreover, even if the digital command signals are synchronized correctly in the transmission phase by the external supervision unit 109, they may reach the driving device 103 of the ultrasound transmission/reception apparatus 101 with delays different from those set forth in the design stage, for example on account of different paths of propagation of the same signals. The lack of synchronization of the digital command signals may result in errors and potentially be harmful in some operating situations.
Further approaches encode the sole indication of start of the transmission phase by the level of a digital control signal. For example, this may be switched from a first value to a second value for a pre-set number of clock pulses. However, the present Applicant has realized that this approach may also be subject to risks of errors and malfunctioning, in particular due to possible erroneous readings of the level of the digital control signal (e.g., due to glitches or spurious pulses that may be present), or to a failure in reading the same digital control signal (e.g., as a result of an incorrect synchronization of the clock).